Geochemistry and Geochronology of Southern Norilsk Intrusions, SW Siberian Traps

Abstract

The Norilsk ore region is characterized by the occurrence of numerous intrusions comprising the PGE–Cu–Ni deposits. The Turumakit area, within the Southern Norilsk Trough, also contains many mineralized mafic intrusions of probably similar economic potential to the known Norilsk deposits. We study igneous rocks from three boreholes within the Turumakit area, sampling gabbro-dolerites and trachydolerites related to the Norilsk and Ergalakh complexes, as well as an outcrop of the Daldykan gabbro-dolerite intrusion. Our petrographical, mineralogical and geochemical data, as well as the U–Pb dating of extracted baddeleyites and zircons, primarily discriminate between the sub-alkaline rocks of the main Turumakit area and the Ergalakh trachydolerites located in the Norilsk and Talnakh ore junctions. Coarser grained Turumakit trachydolerites (with pegmatite segregations) contrast finer grained Ergalakh trachydolerites by having: (1) higher TiO2 (up to 5.5 wt %) compared with 2.2 wt %–3.3 wt % in the typical Ergalakh rocks; (2) low U, lower La/Yb and La/Sm ratios (5–7), in contrast to 8–10 ppm, 2.5–2.6 and 3.0–3.3, respectively, for the Ergalakh trachydolerites; and (3) their age was determined by U–Pb methods on baddeleyite and zircon (244.8 ± 2.7 Ma), and it appears likely that the mafic rocks traditionally attributed to the Ergalakh complex within the Turumakit area are younger than the Norilsk intrusions (250 ± 1.4 Ma). These data strongly indicate an emplacement of Turumakit intrusions during the end of a ~5 Myr magmatic evolution of the Norilsk district. It is therefore proposed that the sub-alkaline rocks of the Turumakit area belong to a separate intrusive complex within the Norilsk district.

The Influence of the Permian-Triassic Magmatism in the Tunguska Basin, Siberia on the Regional Floristic Biota of the Permian-Triassic Transition in the Region

“…This suggests a complicated internal structure of the multilayers and their different origin during at least a half-million or more years (Figure 3A). A similar case was reported recently in the Norilsk region, where the Norilsk-type layered intrusive has been intruded into the Ergalakh intrusive complex (considered to be late Permian) and thus the latter is interlayered with the former timewise in an upside-down position (Figure 3C) (Sereda et al, 2020). All this suggests that to recognize the true age of the geomagnetic secular variation, their measurements and the radioisotopic dating must be obtained from the same samples.…”

“…Distribution of coals from Cherepovskiy (2001); distribution of traps and their thickness and the chroniostratigraphic position of sills and intrusions in left column (1) according to Krivolutskaya (2016), Rad'ko (2016), Ryabov et al (2014) and in right column (2) by Burgess and Bowring (2015). (Distler et al, 1999) Norilsk-1 intrusion [data from Burgess and Bowring (2015)] (B), Stillwater Complex (Wall et al, 2018); (C), the relationship of Norilsk and Ergalakh intrusive complexes in Kuramakit area (modified from Sereda et al, 2020), where the younger Norilsk intrusive complex intruded within and underneath the older Ergalakh complex.…”

“…FIGURE 3 | Chronostratigraphic summary of high-precision U-Pb dating results of zircon from intrusive rocks of the mixed superposition (crosscutting intrusive layers) at Norilsk-1 intrusion and Neoarchean Stillwater Complex of Montana. (A), distribution of U-Pb ages in well G22,(Distler et al, 1999) Norilsk-1 intrusion [data fromBurgess and Bowring (2015)] (B), Stillwater Complex(Wall et al, 2018); (C), the relationship of Norilsk and Ergalakh intrusive complexes in Kuramakit area (modified fromSereda et al, 2020), where the younger Norilsk intrusive complex intruded within and underneath the older Ergalakh complex.…”

Petrographical and Geochemical Characteristics of Magmatic Rocks in the Northwestern Siberian Traps Province, Kulyumber River Valley. Part II: Rocks of the Kulyumber Site

“…It should be noted that the initial isotopic characteristics of intrusive complexes from the Kuluymber river valley were close to those obtained previously for the complexes of the same name sampled in other areas of the Norilsk region. Thus, the subalkaline trachydolerites of the Ergalakhsky complex from the northern and southern parts of the Norilsk district had neodymium composition nearly the same: εNd within −3.8 and −4.2 [67][68][69] and only the initial strontium isotopic composition, 0.7064-0.7075, was slightly higher than the value we measured in sample X-40.…”

Petrographical and Mineralogical Characteristics of Magmatic Rocks in the Northwestern Siberian Traps Province, Kulyumber River Valley. Part I: Rocks of the Khalil and Kaya Sites

“…Karpinsky Russian Geological Research Institute (VSEGEI), St. Petersburg, Russia (analyst B.V. Belyatsky). Chemical separation of elements was carried out by chromatographic method on ion exchange columns according to the method described earlier [57] and the procedure of isotopes measurement was described in [57]. Compositions of rock-forming minerals were analyzed using an electron microprobe CAMECA SX 100 at Vernadsky Institute of Geochemistry and Analytical Chemistry of RAS (analyst N.N.…”